The invention relates to protective packaging of filamentary material to prevent damage during transit and more particularly to a carrier for a plurality of protective envelopes each containing a filament in the form of a coiled optical fiber.
Communication systems have for decades relied upon signal transmission using networks of cables containing copper wires. Arrival of the era of broadband transmission has produced a transition to optical fiber waveguides as the basic conduits of communication signals. Increasing use of optical fiber networks typically translates into increased demand for optical fiber and related products to satisfy expanding telecommunications systems, particularly those involving on-line access. This requires that product suppliers accelerate their output rate and assembly to deliver products and systems according to the demand. Although frequently overlooked, the design of packaging used for product delivery may facilitate the further processing of a product at a receiving location. Suitable integration of production operations between manufacturing facilities leads to efficiency in the processing of optical fiber and related devices intended for use in communications systems.
Optical fiber communication networks frequently include refractive index gratings, also known as optical fiber Bragg gratings. Bragg gratings perform a number of functions related to control and wavelength selection of light within an optical fiber. A common way to incorporate a Bragg grating into a communication line requires splicing or connecting an optical fiber Bragg grating into a section of an optical fiber line. The optical fiber Bragg grating is usually less than ten meters in length.
Optical fibers are predictably brittle since they have the properties of glass. Any device using glass as the primary material of construction requires careful handling during manufacturing and transportation. For this reason current methods for shipping optical fiber Bragg gratings rely upon individual shipping packages containing optical fiber coils wrapped around somewhat flexible cardstock in the shape of circular discs. Upon receipt, by a customer, each coiled optical fiber Bragg grating requires individual handling and testing, as needed prior to incorporating the device into e.g. an optoelectronic assembly.
Current forms of shipping packages do not take into account either the steps of manufacture of an optoelectronic assembly or the space available at a manufacturing station to accommodate a number of loose packages containing optical fiber coils. Consequently, inspection and manufacture of devices using refractive index gratings, such as Bragg gratings, has little compatibility with high volume processing of devices. For this reason, there is a need for packaging of filaments, exemplified by optical fiber Bragg gratings, to facilitate inspection and volume manufacture of assemblies containing these filamentary products.
The present invention provides a carrier for a plurality of individually coiled filaments each contained in a protective envelope. Materials used for filament carriers according to the present invention preferably have properties suitable for use in clean room environments. A carrier according to the present invention has a structure and size that may be varied for compatibility with inspection and processing of filamentary devices held and protected by the carrier. Preferably the filamentary devices are optical fiber devices particularly optical fiber Bragg gratings.
A filament carrier according to the present invention varies from a substantially planar structure having organizing projections protruding from its surface to a more complex rectangular carrier, having ends and sides, produced during molding of a plastic resin. The complex carrier structure may include an elevated platform having an upper surface, a first end, and a second end. A stepped ledge lies on each side of the raised platform. The platform includes a plurality of evenly spaced projections formed adjacent to each stepped ledge. This places a row of projections close to the ledges. The rows of projections are parallel to each other. Preferably there is a retaining rail on each stepped ledge between the side of the carrier and the raised platform. Retaining rails may be either applied to the carrier surface or be molded into the structure. The retaining rails have a parallel orientation with the rows of projections. In addition the carrier may include reinforcement molded into at least one end for increased rigidity.
The evenly spaced projections have a separation from each other that is wide enough to receive the corner of a rectangular envelope. Envelope size and shape may vary depending on the size of a coil of filament and the dimensions of a carrier according to the present invention.
An envelope holds and protects a coil of filament, which is preferably an optical fiber coil. A gap between the rows of projections is wide enough to allow a rectangular envelope to lie flat on the platform with diagonally opposite corners extending into the space between a pair of projections in each row. The evenly spaced projections represent multiple pairs of projections that provide space to retain envelope corners. This allows the carrier to act as a container for a plurality of overlapping envelopes, each containing a filament coil, preferably an optical fiber coil.
Each optical fiber coil includes pigtail ends extending in exposed fashion from diagonally opposed corners of an envelope. Placement of an envelope between projections, as previously described, directs the pigtail ends towards the retaining rails. The retaining rails contain gripping slits into which pigtail ends may be inserted to protect them from contact and inadvertent damage. With suitable position in the gripping slits, the pigtail ends may be made available for connection to monitoring equipment, such as a spectrum analyzer, when the filament coil, in the form of an optical fiber, contains a refractive index grating or Bragg grating. The need to monitor an optical fiber device, such as a Bragg grating, advantageously may use sufficient optical fiber connectors, on the surface of the carrier, to connect the number of fiber coil envelopes held by a carrier.
The size of the carrier may vary depending on the number of envelopes needed, or the amount of space that may be available at a manufacturing station during the assembly of optoelectronic systems that contain optical devices such as Bragg gratings. Regardless of the size or space available in a given carrier there is frequently a need to pre-screen optical fiber devices to evaluate their properties before installing them in costly optoelectronic systems.
A structure of several tiers of carriers may be used to increase the number of filament coils that may be transported in a single package. Using a footprint of 10 inchesxc3x9714 inches for its base, a preferred carrier will hold up to thirty envelopes containing filament coils. Multiples of each set of thirty envelopes result from stacking carriers one on top of another. The present invention includes the formation of stacked carriers in a covered container.
A carrier for coiled filaments, according to the present invention may be referred to as a carrying tray comprising a substantially planar base having a longitudinal axis. The carrying tray includes a first row of projections having spaces between them so that the first row of projections extends above the substantially planar base parallel to its longitudinal axis. Similarly, a second row of projections having spaces between them extends above the base parallel to the first row of projections and the longitudinal axis of the carrying tray such that there is a separation between the first row of projections and the second row of projections.
The carrying tray may further include a first rail of resilient material and a second rail of resilient material mounted on the substantially planar base parallel to the first row of projections. In addition, the carrying tray may have a plurality of rectangular envelopes arranged on the substantially planar surface between the rows of projections. Each envelope includes a first corner opposite a second corner. Also, the plurality of envelopes has a size for mounting in overlapping relationship on the substantially planar base. In this arrangement, each of the first corners is located in a space of the first row of projections, and each of the second corners is located in a space of the second row of projections.
A carrier for at least one coiled filament, according to the present invention may comprise at least a first pair of spaced apart projections, and at least a second pair of spaced apart projections parallel to the at least a first pair of spaced apart projections. At least one envelope to contain a coil of filament is placed between the at least a first pair of projections and the at least a second pair of projections, The at least one envelope has corners sized for retention between the first pair and the second pair of projections. Opposing corners of each envelope may have at least one opening formed therein to allow ends of a filament to protrude from the at least one envelope. The carrier may further include a first rail of resilient material adjacent to the first pair of spaced apart projections and a second rail of resilient material adjacent to the second pair of spaced apart projections. The first rail includes retention slits and the second rail includes retention slots to receive ends of a filament protruding from the openings in the opposing corners of the at least one envelope. A rail may be made from polymeric elastomers, rubbers, and open or closed cell foams.
More particularly a carrier comprises a molded base having a longitudinal axis and including a first end having a reinforced edge, a second end, and a first ledge opposite a second ledge. A raised platform fills a width between the first ledge and the second ledge. There is a first row of projections, having spaces between them, extending above the raised platform adjacent to the first ledge of the base. A second row of projections, also having spaces between them, extends above the raised platform adjacent to the second ledge of the base, such that the second row has a parallel relationship to the first row of projections and the longitudinal axis of the base.
A plurality of rectangular envelopes each has an internal space for a filament and includes a first corner diagonally opposite a second corner. These first and second corners have openings formed in them to expose the ends of a filament extending from the corners. The plurality of envelopes has a common size to mount in overlapping relationship on the raised platform with each first corner located in a space of the first row of projections, and each second corner being located in a space of the second row of projections. A first rail of resilient material, mounted on the first ledge, includes a plurality of slits such that each slit receives an end of a coiled filament that extends from the opening of the first corner of each envelope, so that each slit retains an end of a coil of filament in the first rail. Similarly a second rail of resilient material, mounted on the second ledge, includes a plurality of slots, each to receive an end of a coiled filament, extending from an opening of the second corner of each envelope, so that each slot retains an end of a coil of filament in the second rail.
The following definitions clarify the meaning of terms used to describe the present invention in its various forms and alternative embodiments.
As used herein the term xe2x80x9ccarrierxe2x80x9d refers to packaging items preferably made of plastic and used to organize and hold a plurality of filaments, usually in the form of a coil. A carrier may include at least one plastic envelope.
The terms xe2x80x9cpolymer,xe2x80x9d xe2x80x9cplastic,xe2x80x9d and xe2x80x9cresinxe2x80x9d may be used interchangeably herein for reference to materials suitable for forming carriers and envelopes according to the present invention.
The term xe2x80x9cbasexe2x80x9d identifies a support component of a carrier. Preferably a base is molded by thermoforming, injection molding or other well known method for forming molded structures.
A xe2x80x9ccarrying trayxe2x80x9d refers to a carrier without including an envelope.
The term xe2x80x9cenvelopexe2x80x9d means a substantially flat container, preferably comprising a plastic film having a space to accommodate a filament between layers of film. Suitable films include those including cushioning air pockets or similar features to protect fragile filaments such as optical fibers.
A xe2x80x9cprojectionxe2x80x9d is a small post or rod-like element extending from the surface of a base or carrying tray. Projections according to the present invention may vary in cross sectional geometry. Possible cross sections include circular, triangular and square.
The term xe2x80x9cresilient railxe2x80x9d refers to a pliable cushioning material that may be used to retain the ends of filaments, especially fragile filaments, particularly when the filament is an optical fiber. Preferably a resilient rail comprises an elastomer or polymeric structure attached to a base or carrying tray. Alternatively, a resilient rail may be a molded feature formed in a base during the molding of a base.
The terms xe2x80x9cslitxe2x80x9d and xe2x80x9cslotxe2x80x9d are synonymous and may be used interchangeably to refer to parts formed in resilient rails to retain ends of filaments within a resilient rail. A molded resilient rail may include slits/slots.
As used herein, the term xe2x80x9cfilamentxe2x80x9d refers to a thread-like structure that may be packaged in an envelope for shipping. A packaged filament may be in the form of a coiled filament but such form is not considered limiting. Preferably a filament according to the present invention is an optical fiber, particularly an optical fiber having a Bragg grating formed therein.
The term xe2x80x9crecessxe2x80x9d identifies part of a base or carrying tray that is suitably shaped to house a filament connector that provides attachment of filament ends to external systems and devices. Optical fibers, particularly optical fiber Bragg gratings, having connectors attached to their free ends may be connected to inspection equipment to confirm satisfactory conformance to requirements. The present invention preferably uses recesses for attachment of filament connectors to carriers. This is only one of several means for attaching filament connectors. Others, for example, may include adhesive attachment or the use of a class of interference connectors that includes hook and loop fasteners.